I use Livestats but unfortunately I dont know Webtrends so dont know how much help I can be.
The package itself does seem to do all the usual stuff but I do use MSAccess on logfiles to get IP addresses. The Watches in the 'virtual Admin' area are well worth the setup effort. These let you watch and track visiters by IP and URL or track links(out) via the Click-Thru Watch which seems to be ideal for reseller links.
I got lots of info on Livestats from the Fasthosts (abuse) forum but this may not be relevant as much of discussion is based around their particular setup.